JP2588275B2 - Secondary excitation device for AC excitation synchronous machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an AC-excited synchronous machine having an increased system frequency control (AFC) adjustment range during operation of a generator of a pumped storage power plant.
The present invention relates to a secondary excitation device.

[Prior art]

Recent power systems have been operating late at night due to an increase in the ratio of nuclear power and an increase in the number of daily starts and stops of thermal power.
Insufficient AFC adjustment capacity has necessitated input adjustment of pumped storage power plants as a response. Fig. 5 is IEEJ, 107, 3
No., Sho 62, Minato, and Mimatsu It is a typical circuit configuration diagram of the conventional variable speed power generation system shown in "Variable speed hydropower generation system". In the figure, 1 is an AC excitation synchronous machine (hereinafter abbreviated as AESM). , 2 is a rotor (secondary coil), 3 is a reversible pump turbine, 4 is a shaft, 5 is a transformer for an excitation converter, 6 is a converter for excitation (hereinafter abbreviated as EX), 7 is A rotational phase detector (resolver), 8 is an EX controller, and 9 is a harmonic suppression filter. Next, the operation will be described. First, the AC excitation synchronous machine (AESM) has a structure in which three-phase windings are distributed and stored in an equilibrium because it is necessary to create a magnetic field that rotates electrically on the rotor 2. In order to operate the AESM at a variable speed, an excitation side (rotor side) control method in which the AESM is secondarily excited by EX6 is usually adopted. This control method corrects the frequency by the secondary excitation by the amount of slip so as to match the system frequency even if the rotational speed changes, and thus enables parallel operation with the system. As the EX6, a cycloconverter system that produces an AC directly from an AC is used. That is, the EX 6 takes in the commercial frequency AC power through the excitation converter transformer 5 for the power supply, replaces it with a low frequency AC of several Hz, and supplies it to the AESM rotor (secondary coil) 2. Also, the output signal (phase detection signal) of the resolver 7
Is supplied to an EX controller 8 which performs an operation by a microcomputer, and is used for a thyristor gate control of EX6, a governor control signal for controlling the reversible pump turbine 3 and the like. The EX controller 8 is controlled so that the active power command, the reactive power command, the voltage, and the optimum rotational speed set as shown in FIG. 4 are obtained.
Drive AESM.

[Problems to be solved by the invention]

Since the secondary excitation device of the conventional AC excitation synchronous machine is configured as described above, the power factor on the power supply side of the excitation converter is poor, and the complicated configuration of the excitation converter transformer and the AC excitation synchronization There is a problem that the installation space of the apparatus becomes large due to the large capacity of the machine and the like, and the entire AC excitation variable speed system is uneconomical. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to improve the circuit configuration of the excitation converter and the control method, thereby achieving AC excitation synchronization capable of AFC adjustment during economical pumping operation. The purpose is to obtain a secondary excitation device for the machine.

[Means for Solving the Problems]

The secondary excitation device for an AC excitation synchronous machine according to the present invention is configured such that the excitation converter is constituted by a converter and a forced commutation type inverter, and the inverter is controlled by switching between start-up and operation of the inverter. An operation / start switching circuit for giving a control command to the inverter, and a start frequency command circuit for switching the operation / start switching circuit to the starting side when starting the inverter and instructing the inverter to gradually start the AC excitation synchronous machine. After a predetermined time from the start of the inverter,
The start switching circuit is switched to the operation side and the inverter controls the AC excitation synchronous machine by converting the output three-phase current into two axes, d and q axes, to control the AC excitation synchronous machine. An inverter control unit that executes an operation based on a command, and a control unit of an excitation converter that performs DC output voltage constant control and power supply side power factor approximation of 1.0 for the converter.

[Action]

The excitation converter according to the present invention is configured to include a forced commutation type inverter and a converter, and the inverter is subjected to power control and optimum rotational speed control, and
The converter is controlled so that the power factor becomes 1.0 and the output voltage constant control is performed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those in FIG. 5 are denoted by the same reference numerals, and in FIG. 1, 6-1 is the inverter of EX6, 6-2 is the converter of EX6, and 10 is the power on the power supply side of converter 6-2. This is a power factor improvement circuit that controls the rate to 1.0. Next, the operation will be described. First, a control command such as an active power command, a reactive power command, a voltage, and an optimum rotational speed input to the EX controller 8 generates a control command for controlling the inverter 6-1. A variable frequency AC power is supplied to the slave 2. On the other hand, the power factor improving circuit 10 controls the converter 6-2 so that the power factor on the power supply side of the converter 6-2 configured independently of the inverter 6-1 always approaches 1.0. (In the conventional cycloconverter system, the power factor control cannot be performed independently because the converter unit is not independent, so the normal power factor is very low, about 0.2.) FIG. 2 shows an example of the waveform of each unit of the present invention. It is shown. FIG. 6 shows an example of waveforms of various parts of the conventional cycloconverter system. As shown in FIG. 2, when the power factor improving circuit 10 controls the power factor to approximately 1.0, the output side of the inverter 6-1 a. The AESM side and the input side of the converter 6-2 (b. ) Voltage and current are clearly EX controller 8
The effect of the waveform improvement due to this is remarkably exhibited. That is, there is no phase shift between the voltage and the current. Especially the sixth
In comparison with the conventional example shown in the figure, in the case of FIG. 2, it can be seen that the result of the power factor improvement clearly appears in the phase difference between the voltage and the current on the power supply side. Also, it can be seen that in the conventional cyclone converter system, the configuration of the transformer for exciting converter 5 on the circuit is complicated, whereas in the present invention, the structure is extremely simplified. This converts EX6 into inverter 6-1 and converter 6-
This is due to the fact that the configuration is completely separated from that of the second embodiment. Further, b. In the case of the present invention, the waveform on the power supply side also has a small ripple content, so that the capacitance of each filter becomes small. Further, a GTO (gate turn-off) element 20 is used in the power circuit of the present invention. When the GTO element 20 is adopted, parallel and series snubber circuits (surge suppression circuits) 21 and 22 are required, so that the losses of the snubber circuits 21 and 22 are large. Therefore, by providing the snubber energy regeneration circuit 23 as shown in FIG. 3, the loss can be suppressed to a small value.
In the figure, 24 is a snubber capacitor, 25 is a snubber reactor,
26 is an auxiliary GTO, 27 is a CT (current detector), 28 is a series capacitor, and 29 is a flywheel diode. FIG. 3 is a detailed view of a main part of the inverter circuit 6-1 taken out from one arm. Further, in the above-described embodiment, the forced commutation type 12-phase voltage converter has been described by taking the converter 6 for excitation as an example, but may be a polyphase type instead of a 12-phase type. Further, a one-side forced commutation type may be used. Next, FIG. 4 shows another embodiment of the present invention. The figure is a block diagram of the secondary excitation device of the AC excitation synchronous machine. In the figure, 11 is an inverter control unit, 12 is a current transformer that detects a system current, 13 is a transformer that also detects a system voltage,
14 is an active power and optimum rotational speed control unit, 15 is a voltage and reactive power control unit, 16 is a (d, q) axis control unit for phase, 17 is an operation / start switching circuit, and 18 is a start frequency command circuit. . Next, the operation will be described. First, in this case EX6
6-1 is controlled by the active power and optimum rotational speed control unit 14 to completely separate the inverter from the forced commutation type polyphase inverter and the converter, and the converter 6-2 controls the output voltage constant and the power supply side power factor. The control is divided so that it becomes 1.0. The inverter control unit 11 mainly takes in the active power, the optimum rotational speed control unit 14 and the voltage, the control command from the reactive power control unit 15 and the phase signal detected by the resolver 7, and outputs the three-phase current of the AC excitation synchronous machine. d and q axis conversion
An operation for performing the active power, the optimal reactive power, the voltage, and the optimal rotation speed control is performed. Also, at the time of starting, the operation / start switching circuit 17 is switched to the b (start) side, and the operation of the inverter 6-1 is started by a command from the starting frequency command circuit 18 to gradually accelerate the AESM. After that, the operation / start switching circuit 17 is switched to the a (operation) side to start the normal operation. Further, a signal serving as a reference for phase control is detected by the resolver 7 to generate a difference between the system frequency and the rotation speed, and the magnitude and phase of the exciting current are controlled by the inverter 6-1 based on the reference signal. To the rotor 2 to finally control the voltage and power of the stator 1. In the above embodiment, the forced commutation type multi-phase voltage inverter has been described as an example of the converter 6 for excitation. However, the forced commutation may be a single-sided or double-sided forced commutation type, or may be a parallel multiplex. Also, voltage type or current type may be used.
The element may be a GTO, a transistor, or another element, and has the same effect as the above embodiment.

【The invention's effect】

As described above, according to the present invention, the AC excitation synchronous machine 2
Since the secondary excitation device is configured to use a forced commutation type voltage-type converter as the excitation converter or to use a forced commutation type inverter and converter, the power factor on the power supply side is set to 1.0. This makes it possible to reduce the capacity of the AC excitation synchronous machine and to obtain an economical one that can simplify the circuit configuration.

[Brief description of the drawings]

FIG. 1 shows an AC excitation synchronous machine 2 according to an embodiment of the present invention.
FIG. 2 is a block diagram of a secondary excitation circuit, FIG. 2 is an explanatory diagram of a main part waveform of the present invention, FIG. 3 is an explanatory diagram of a snubber energy regenerating circuit of the present invention, and FIG. 4 shows another embodiment of the present invention. FIG. 5 is a block diagram of an inverter control unit, FIG. 5 is a block diagram of a secondary excitation circuit of a conventional AC excitation synchronous machine, and FIG. In the figure, 2 is a rotor, 3 is a reversible pump turbine, 6 is a converter for excitation, 6-1 is an inverter, 6-2 is a converter, 8 is a controller of the converter for excitation, 10 is a power factor improvement circuit. , 11
Is an inverter control unit, 14 is an active power and optimum rotational speed control unit, 15 is a voltage and reactive power control unit, 17 is an operation / start switching circuit, and 18 is a start frequency command circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A secondary excitation device for an AC excitation synchronous machine configured to perform a variable speed operation by controlling a rotor of an AC excitation synchronous machine directly connected to a reversible pump-turbine by an excitation converter. The converter for use is composed of a forced commutation type inverter and a converter, and in order to control the inverter by switching between start and operation, the operation / start switching circuit for giving a control command to the inverter, and the inverter A starting frequency command circuit for switching the operation / start switching circuit to the starting side and instructing the inverter to gradually start the AC excitation synchronous machine; and To control the AC excitation synchronous machine by converting the output three-phase current to the d- and q-axes for the inverter and controlling the AC excitation synchronous machine. AC excitation, comprising: an inverter control unit that executes a calculation based on a command; and a control unit of an excitation converter that performs constant DC output voltage control and power supply side power factor approximation of 1.0 for the converter. Secondary excitation device for synchronous machine.